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Bioremediation - 7 - 10 September 1.993 <br /> 3. Biological Screening <br /> a. Sail/contaminant matrix (clay, sand, silt, organic matter - adsorption/desorption rates - <br /> clays and organic matter adsorb hydrocarbons) <br /> b. Salinity or EC (high salinity inhibits bioremediation) <br /> C. pH (high and low pH inhibit bioremediation) <br /> d, Temperature (high and low temperatures inhibit bioremediation) <br /> C. Toxicity - metals, organic contaminants, etc. <br /> f. Microbial population and total numbers <br /> 4. Treatability Testing <br /> a. Initial Testing - organic analyses, leachable fractions of contaminants, suit particle size <br /> distribution, aquifer pumping tests, site hydrology determination, organic matter <br /> content, oxygen demand, moisture retention curves, total nitrogen, inorganic nitrogen, <br /> phosphorus, EC, pH, initial biological characterization, measurement of numbers and <br /> response to 5-day incubation in stirred flasks <br /> b. Liquid-Solids Treatment Test -measure end-point achievable using duplicate stirred <br /> reactors <br /> C. Solid-Phase Treatment Test - sail pan test <br /> Benefits of In-situ Bioremediation <br /> 1. 1.ow capital and operating costs <br /> 2. Minimal specialized equipment <br /> 3. Low profile technology <br /> Real and Potential Drawbacks and Difficulties <br /> 1. Addition of oxygen and nutrients can disrupt ambient inorganic chemistry, causing formation <br /> plugging by precipitates <br /> 2. Some forms of oxygen addition (such as hydrogen peroxide) can be prematurely catalyzed by <br /> dissolved metals <br /> 3. Excessive microbial growth can cause plugging of the formation (easily corrected) <br /> 4. High toxic concentrations of some hydrocarbon contaminants can impede source area <br /> remediation <br /> 5. Indigenous microbial consortia must be adapted to the hydrocarbon contaminants and be <br /> capable of degrading the contamination to sufficient concentrations (biostimulation) <br /> b. Some indigenous microbes may be pathogens or produce undesirable side-effects <br /> 7. Nan-indigenous microbial consortia must be able to survive in the environment and compete <br /> with indigenous consortia for food and nutrients (bioaugmentation) <br /> 8. Periodic reinoculations of non-indigenous consortia along with nutrients are probable <br /> 9. It is difficult to determine whether bioremediation is working and when it is complete <br /> 10. Heterogeneity in the subsurface can be problematic because inconsistent distribution of <br /> contaminants, oxygen, and microorganisms, and heterogeneous physical properties disrupt <br /> bioremediation activities <br /> 6i ' d 800' oN ££=6 £6` 9T dog DN ]31 <br />